This invention relates to an iontophoretic bioelectrode method and apparatus and more particularly to such a method and apparatus in which migration of ions from the apparatus to a person's skin or skin barrier is inhibited in certain directions.
Iontophoresis is a technique of delivering ions into a person's skin or tissue by placing a solution or other medium containing the ions in contact with the skin, and applying electric current to the medium. The solution or medium containing the ions is typically carried by a first bioelectrode pouch or receptacle. Ions are caused to migrate from the ion carrying medium through the skin or tissue by the application of the electric current to the medium, and by placement against the skin of a second bioelectrode within some proximity of the first bioelectrode and the application of current of opposite polarity to the second bioelectrode. This technique has been discussed in a number of prior art patents including U.S. Pat. No. 4,141,359 and 4,166,457. Examples of bioelectrodes which are generally useful for making electrical contact with the skin are described in U.S. Pat. Nos. 3,862,633, 3,945,384 and 3,973,557.
There have been several bioelectrode proposals for carrying the ion solution or medium and placing it in proximity with the skin including provision of a receptacle with a wetable barrier on one side thereof. The wetable barrier or wall is covered until time of use and then uncovered for placement against the skin. Then, upon application of the electrical current, the ions migrate through the wall into the skin.
Another proposed arrangement involves the use of a receptacle having a microporous membrane on one side thereof which may be placed in contact with a person's skin. The membrane is selected so that it will not leak prior to use, but will allow migration of ions therethrough to the skin upon application of an electric current to the ion-carrying solution. With this arrangement, less care need be given to storage, transport and use of the receptacle since the ion containing fluid will not leak as it is used.
One of the principal problems with the prior art devices has been the problem of the bioelectrode producing burns at the site of application of medications. If the current to the bioelectrode is too high, the resistance of the skin or tissue may result in burns or other tissue damage. Further, once the skin or tissue is burned, the resistance at the site of the burn decreases allowing for an increase in current flow and thus ion migration at that site and this compounds the danger of serious burns to the skin or tissue. If a blemish or cut exists somewhere at the location of contact of the bioelectrode with the skin or tissue, then the ions tend to migrate toward and concentrate at the blemish thereby increasing the danger of a burn at that site.
One approach to reducing the likelihood of burns to the skin or tissue is to simply reduce the amount of current applied to the bioelectrode. This, however, increases the treatment time for the patient since lower current flow requires longer periods of application to reach the same degree of ion penetration. Of course, it would be desirable to both minimize the treatment time and minimize the likelihood of burns to the patient from the treatment.